A magnetic resonance imaging (MRI) system is mainly comprised of a magnet system, a spectroscopy system, a computer system and an image displaying system. Wherein, the magnet system has a function of generating a magnetic field having a degree of non-homogeneity less than 1 ppm within a spherical volume of 500 mm. Currently, the nuclear magnetic resonance imaging system has a magnetic induction generally ranging from 0.35 tesla (T) to 3 T, and has been widely used in hospitals all around the world. However, the MRI system with a magnetic induction above 7 T primarily has applications in scientific researches. The MRI signal intensity has a decisive influence on the signal-to-noise ratio of an image, while the signal intensity is substantially in a square proportion to the magnetic field intensity. Thus, enhancing the magnetic field intensity has become the most important development goal for MRI technology.
With the development of superconducting magnet and cryogenic technology, advanced fabrication technique and massive numerical optimization technique have been applied to magnetic field analysis and fabrication of nuclear magnetic resonance magnet systems. By combing a super computer with a superconducting magnet system for nuclear magnetic resonance with a high magnetic field, visualization of the overall system can be achieved. The massive information obtained by nuclear magnetic resonance with a super-high magnetic field is processed rapidly by the super computer so as to achieve a rapid diagnosis of a molecular level, thereby achieving a modern diagnostic equipment that is indispensable in the clinical imaging diagnosis. Due to new functions brought in by the super-high magnetic field, the magnetic resonance imaging technology plays a more and more important role in the field of life detection, which can, by means of image, demonstrate the metabolic process of a human body, detect the mechanism of the nervous system, probe human diseases in very-early phase, or the like. With the rapid development of computer technology, currently, it is possible to reconstruct a four-dimensional magnetic resonance image of a super-high resolution by means of the ultra-high speed of computing capability of a computer, and to perform a multi-scale human body simulation. The combination of a super computer with a magnetic resonance imaging with a super-high magnetic field forms a so-called concept of super magnetic resonance imaging.
In the aspects of life research and clinical application, a higher sensitivity to blood flow signal and degree of oxygen utilization can be obtained, molecules of low concentration contents can be more accurately detected, and an environment in which molecules “inhabit and gather” can be precisely positioned in high-field craniocerebral MRI. MRI of a super-high magnetic field intensity can obtain a higher resolution. With the development of higher magnetic field MRI and a better array or superconducting coil, a resolution of a level of 1 mm that is currently and frequently used in clinic can be advanced to 300 μm, or even 100 μm, such that a better contrast and richer image information can be obtained. Under a high resolution and a super-high magnetic field, more colorful fine structures can be observed, in addition to original dispersion, perfusion, functions or the like. The increase of the amount of information will exceed the pure increase of resolution, which may become unaffordable for imaging experts. Thus, how to more automatically handle and integrate such massive information so as to assist a more rapid and accurate diagnosis as well as an early predication has become more and more important.
The superconducting magnet with a high degree of homogeneity has a high magnetic field stability, so that it can be adapted to user's needs and provide various magnetic field configurations and spatial distribution characteristics of magnetic field. For example, a combination of a plurality of coaxial solenoids can achieve an asymmetric magnet of a high degree of homogeneity, forming a superconducting magnetic resonance imaging system with two or more homogeneous regions of high magnetic fields and high degrees of homogeneity. Currently, the nuclear magnetic resonance magnet developed and applied at home and abroad has a magnetic induction from 1.5 T to 3 T. As for the nuclear magnetic resonance magnet system with a high magnetic field and a high degree of homogeneity, it is still under study and development.